The invention of portable night vision technology such as
helmet-mounted night vision systems has opened a new dimension in modern
warfare. They have allowed those who possess such systems to 'own
the night' and remove the cover of darkness as the camouflage of
their enemies. Helmet-mounted night vision is indispensable for any army
or special forces unit contemplating operations, and these days, whoever
owns the night can often rule the day.

Night vision systems are very much a product of the post-Second
World War environment. Night operations were difficult and dangerous for
all the belligerents during World War II and while night vision
technology was actively researched by both the Axis and Allied powers,
sufficient miniaturisation would not have been achieved to allow any
mounting onto an individual infantry soldier's helmet. Fast-forward
sixty years and television pictures filmed in the eerie green glow of
the night vision camera are commonplace and audiences are now accustomed
to watching footage of combat operations performed under the cover of
darkness.

Night Vision Principles

Traditional systems work on a simple principle: they detect light
emissions in the 'near-infrared' band. As a comparison the
human eye sees light in the wavelengths of 0.4 to 0.7 micrometers,
whereas night vision systems can detect light in the range of one
micrometer. Essentially, the sensor detects ambient light and amplifies
it. During night time this ambient light can come from starlight or
moonlight and it is this light that is reflected from objects and
displayed by the system.

Image intensifier goggles absorb photons of ambient light that hit
a detector plate located in an intensifier tube. This detector plate
will then emit a cascade of electrons and these then collide with a
phosphor screen. The collision of these electrons produces light at the
point where they strike the screen and this subsequently creates an
image. So why is the image usually green? Simple: most systems use a
green phosphor screen because the human eye sees this colour
particularly clearly.

The military generally uses passive systems. They are passive in
the sense that they use the ambient light described above as their
source of illumination. Active systems are available but these require a
light source, usually infrared, to illuminate the surroundings. However,
infrared can be detected; and for this reason passive systems are more
attractive for military applications. That said infrared-based active
systems have developed a niche for civilian security camera
applications. Most modern systems are not without active illumination
systems. For instance, night vision goggles often have a small infrared
light which can be shone downwards to read a map.

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The earliest passive systems arrived during the Vietnam War. These
systems were put into the bracket of so-called
'generation-one' capabilities. They were large, depended on
good moonlight coverage to work, and would provide light amplification
of around 1000 times the ambient levels. Compared to modern
generation-three (gen-three) systems, these early goggles often suffered
from image distortion.

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Gen-two systems could take the light amplification to around 2000
times more than the ambient level, and with this the quality of the
image improved along with the overall reliability of the designs. These
systems began to appear around the late 1960s and early 1970s and could
see the environment in light conditions that were equivalent to
one-quarter of the illumination provided by a full moon. One of the
first notable gen-two systems was ITF's AN/PVS-5 Night Vision
Goggle (NVG) system.

The technological quantum leap has come with the gen-three systems.
These amplify light up to 50,000 times the ambient levels. Gen-three
systems have also seen a huge increase in service life. These designs
now have a life expectancy of up to 10,000 hours, compared to the 2000
hours of the first generation and the 4000 hours of the second.

Product Survey

The beauty of early systems, such as the AN/PVS-5 design, lies in
their versatility. These goggles can equip everyone from infantry
soldiers to drivers and platoon leaders: and they can be used in either
a helmet-mounted or a hand-mounted fashion. They also have a built-in
active infrared system for very short-range illumination.

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ITT manufactures the AN/PVS-5 and AN/PVS-7. The latter are
regularly seen on the helmets of soldiers based in Iraq, although they
earned their spurs in Operation Desert Storm eleven years earlier. They
will eventually replace the AN/PVS-5 systems in US Marine Corps service
following a 2005 contract to this effect. One of the key benefits
provided by the AN/PVS-7 system over earlier designs is their light
weight: 540 grams vs. the 850 for the AN/PVS-5: a load savings that
significantly reduces fatigue. As with the AN/PVS-5 system, the -7s have
a close-range infrared light.

Northrop Grumman is the other American brand leader in the
helmet-mounted night vision system market. The company produces the M963
system, which has integrated infrared light source for short-range
illumination. The goggles have been designed not only for dismounted
soldiers, but also for night time driving. The N963 goggles are powered
by conventional AA-size batteries helping to reduce weight. They also
have an automatic brightness control.

Moreover, the company builds an M966 four-times magnification
goggle unit. These are designed for night-time surveillance and as well
as being fitted to an infantryman's helmet, they can also be used
as a hand-held monocular system, or mounted on a tripod. The M961 goggle
system takes the magnification a step further, providing six-times image
intensification, but at a light weight of 1.5 kg

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Northrop Grumman's binocular M953 provides the fidelity that
aviator systems afford to the foot soldier. Not only can the goggles be
used in dismounted operations, but they have also been designed with
amphibious missions and driving in mind. The M953 can be submerged in up
to 20 m (66 ft) of water.

ITT meanwhile produces the AN/PVS14, which unlike the AN/PVS-5/-7,
is a monocular design. This means that while it can attach to the
users' helmet, it also has the capability to be attached to a
weapon sight. Unlike the AN/PVS-5/-7 designs, the AN/PVS-14 is a third
generation device which can provide five-times magnification when used
with optional, attachable lenses. This makes the design especially
useful for reconnaissance and observation operations, where standoff
distance is always welcome.

American special forces are equipped with Northrop Grumman's
M983 monocular system, which can be used in either a helmet-mounted,
weapon-mounted or hand-held capacity. The company designed the M983
product to also be fully compatible with a standard reflex photo or
video camera--a handy addition to night time surveillance or
reconnaissance operations. Furthermore, the company also builds the
monocular M914 system which is as versatile as the M983, but which can
provide three- or five-times image magnification.

One of the latest United States Army acquisitions is the ITT
AN/PSQ-20 Enhanced Night Vision Goggles (ENVG) design. This is a
third-generation product intended to replace the AN/PVS-7/-14. The
AN/PSQ-20 can be used either on its own or with rifle-mounted
laser-sights The ENVG combines existing gen-three technology with
thermal imaging sensors. Like image intensifiers, thermal imagers use a
simple technique. All objects emit a heat signature and the hotter the
temperature, the brighter the image appears on screen. ENVG use these
two techniques since night vision is great at seeing things in the dark,
but still requires an ambient light source, even if it is just
starlight. The thermal imaging system provides extra vision in
conditions where the ambient light source is so minimal that it cannot
be detected by the intensifier. This also avoids the need to use
infrared illumination as the light source. Where the ambient light is
insufficient, the thermal imaging allows the user to see with sufficient
clarity.

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ITT also produces the AN/PVS-23, a binocular based on the AN/AVS-6
NVGs originally designed for pilots. These goggles have an infrared
illuminator that can either be used for spot or flood illumination to
light up a small area. One of the advantages of the AN/PVS-23 is that
its binocular design allows the user to see an independent image through
each tube, rather than types that use a single lens where the image is
then viewed through binoculars. The system can be either helmet-mounted
or removed and used as a pair of binoculars.

In terms of other third-generation systems, ITT builds the
dual-tube binocular MV-14BG which provides good depth perception and is
thus particularly useful for troops driving at night. The MV-14BG system
can be used in either a helmet-mounted configuration or as binoculars.

The binoculars can be detached from one another and used separately
or in conjunction with a camera or weapon sight. Moreover, the goggles
are waterproof down to 20 metres.

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O'Gara of Cincinnati, Ohio manufacturers the AN/PVS-21; a
design popular with American Special Forces. Following an order in
November 2006 the US Marine Corps will be equipped with what the company
calls a 'significant number' of these systems. The AN/PVS-21
can be used in either binocular or monocular configuration and features
an integral 'head-up display'. This allows the user to see a
number of different imagery sources, including video transmission,
thermal imaging or even Global Positioning System data.

The display of a number of imagery sources onto a visor is already
commonplace in military aviation; however, delivering similar
capabilities to the infantry soldier will go a long way to increasing
situational awareness. It also provides a taste of the imagery
capabilities which may appear in several of the 'Future
Soldier' system-of-system programmes earmarked for service entry
over the next decade. In the same year that O'Gara sold its
AN/PVS-21 design to the US Marine Corps; it also secured a contract from
the British Ministry of Defence. This system is also in service with the
Canadian and Italian militaries.

Bushnell builds the lightweight 1 x 20 first-generation NVGs.
Weighing 510 grams, these goggles are some of the lightest of their
kind. They are joined by the Centurion Systems Multitask 1.5 x 24
CS44056 Dep Super Gen Night Vision monocular. This system can be either
hand-held or helmet-mounted or also be attached to a camera to allow the
recording of night vision footage. The Night Phantom dual-tube binocular
is a third-generation system that can be helmet-mounted or head-mounted
and features an adapter to allows it to be fitted to the Mich (Modular
Integrated Communications Helmet), which is replacing the US Personnel
Armor System Ground Troop helmet.

The American specialist N-Vision Optics produces the G-15 HMNV system which claims particularly good depth perception. Depth perception
is particularly important as it allows the user to see a clearer
three-dimensional image without the picture appearing as a
two-dimensional TV-style image. Like the AN/PVS-21, this system has a
dual-tube binocular design. The G-15 can be worn as a helmet-mounted
system, detached and used as binoculars or alternatively separated into
monoculars which can be hand-held, helmet-mounted, fixed on a camera or
mounted on a weapon. The G-15 system includes short-range infrared
illumination and is waterproof down to two metres.

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N-Vision builds the NVP-140 second-generation, single-tube, rugged
binocular which can withstand up to 5Gs of shock. Its sleight 450-grams
allows it to be worn for long periods. A flip-lock mechanism allows it
to be quickly detached for use as hand-held binoculars. Night Vision of
the USA also makes a system that can be converted into variable-range
binoculars. The company's USVN-221G design is water resistant and
features dazzle protection. Optional lenses allow the binoculars to have
x3 magnification.

Russian Night

For many years, the Russians have excelled at night vision
technology and Russian companies offer many robust designs. One example
is the ONV NVG design built by Lomo, which can be used either
helmet-mounted or as hand-held binoculars. The Belarussian SV-23 design
is a first-generation NVG system, weighs 70 grams and its aluminium
construction provides good shock resistance. An infrared illuminator is
included, and optional lenses allow the system to be converted into
binoculars with up to x4.5 magnification. Push-button controls let the
user switch on the in-built infrared illumination.

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Away from Russia, the GNV-2 is built by Night Lights Vision of
South Africa. This second-generation system can provide a
high-resolution image across the 40[degrees] field-of-view and has a
built-in dazzle protection system that prevents the NVGs from being
damaged by sudden light flashes.

The Future

With a range of first-, second- and third-generation systems on the
market, helmet-mounted night vision developers are turning their
thoughts to what technologies we might see in future systems. Presently,
systems use digital data derived from the ambient light as it enters the
tube, which is then converted into analogue imagery by the tube for
display to the user. Allowing night vision goggles to display a digital
signal would help reduce weight and size.

We have already seen a glimpse of sensor fusion via the AN/PSQ-20
ENVG design which utilises both thermal and intensified imaging to
enhance the users' situational awareness. While this technology is
expensive (standard military-grade NVGs cost in the region of $ 2500 per
unit, the ENVG system is projected to cost around $ 8000 per unit), mass
production and technological advances may make NVG systems more
affordable.

One glimpse of the future was seen at the Ausa Winter Symposium and
Exhibition 2007 in Florida: Rockwell Collins showcased what the company
calls its 'Future Force Warrior Headgear System (FFWHS). The design
uses fused imagery but does away with a goggle design. This is replaced
by an image intensification camera fusing both the NV and IR imagery and
which is fitted into an Advanced Combat Helmet and then displayed on the
soldier's monocular display. Like the ENVG system, the FFWHS is
designed to provide the soldier with a range of information such as GPS
or targeting information derived from a command and control network,
along with thermal and infrared imagery. The major challenge with the
present system is its weight, which is around 2.3 kg when the helmet is
included. The system is yet to enter production and is still very much a
technology demonstrator.

Going Colour?

Other technologies on the horizon include 'Colorpath'.
Developed by Tenebraex of Boston, Massachusetts, Colorpath provides the
user with colour night vision converted from the imagery derived from a
standard NVG tube. There are many advantages with such technology. The
company's website lists these as: "Wound assessment,
camouflage detection; vehicle and personnel identification, marking
identification, map reading". In fact, they are almost endless.
Such technology could go some way into making the murky green world
appear more like daylight with all of the visual benefits that the
warrior enjoys when operating in sunlight. While technology is moving in
the right direction in terms of image fusion, colour NVG technology and
digital displays; the real challenge will be in making this technology
light and rugged enough for the warfighter to use, and affordable enough
for the procurement chiefs to buy.

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